Dynamoelectric machines, such as generators, typically employ a stator core comprised of an array of axially extending circumferentially spaced slots formed in a radial inner surface of the stator core. FIG. 1 illustrates a slot 11 in a stator core 10, with coils 12 seated within the slot 11 and held in place by a stator wedge 14, a prestress driving strip (PSDS) 16, and one or more filler layers 18, 20. These support components are employed in order to maintain the coils 12 in a radially tight condition within the slot 10. The coils 12 operate under continuous strain of electromagnetic forces and thus are contained within the slot 10 to prevent insulation damage caused by relative movement between the coils 12 and the stator core 10. The wedge 14, PSDS 16, and filler layers 18, 20 impose radial forces on the coils 12 to aid the coils 12 in resisting magnetic and electrically induced radial forces.
Prior to installing the stator wedge 14 in the slot 11, the PSDS 16 and filler layers 18, 20 are initially positioned over the coils 12. The wedge 14 is then slid over the PSDS 16 and filler layers 18, 20, to test the tightness of the wedge 14. Based on the tightness of the wedge 14, one or more of the PSDS 16 and filler layers 18, 20 may be removed or added, until a desired tightness of the wedge 14 is achieved. For example, if the wedge 14 is too tight and cannot be slid over the PSDS 16 and filler layers 18, 20, the PSDS 16 may be removed. In another example, if the wedge 14 is not sufficiently tight, an additional filler layer may be added. In an example, the wedge 14 is a check wedge with a plurality of openings to insert a device for measuring tightness at each opening and an average of the measured tightness across the openings is used to determine the wedge 14 tightness.
After the desired tightness of the wedge 14 is achieved, the wedge 14 is installed by driving the wedge 14 along axial slots 15 and over the PSDS 16 and filler layers 18, 20. Conventional methods for driving the wedge 14 involve manually providing the force required to install the wedge 14. For example, FIG. 2A illustrates a block 22 and a mallet 24 to manually install the stator wedge 14 in the slot 11 of the stator core 10. The block 22 includes a recess 26 on one end and an angled portion 28 on an opposite end. FIG. 2B depicts that during installation of a wedge 14 into the slot 11, the recess 26 is positioned to engage one end of the wedge 14 within the slot 11, while the angled portion 28 is struck by the mallet 24 to axially drive the wedge 14 over the PSDS 16 and filler layers 18, 20. A clip 30 is used to apply pressure on the PSDS 16 and filler layers 18, 20, to prevent the PSDS 16 and filler layers 18, 20 from bowing up, as the wedge 14 is driven over the PSDS 16 and filler layers 18, 20.
In addition to the manual method discussed above for driving wedges over the PSDS and filler layers in stator core slots, powered tools have been developed for driving filler layers under installed wedges in stator core slots, such as in U.S. Pat. No. 7,707,710 to Lape. As depicted in FIGS. 5 and 7 of Lape, the tool housing is positioned over an installation location, where a foot pulls a filler layer under an installed wedge. As the foot pulls the filler layer under the installed wedge, the tool housing presses down on the installed wedge, to reduce radial vibrations of the filler layer, as it is driven under the installed wedge.